The word "selfish" and "selfishness" are the two most maligned words in the English language. We commonly use them to denote "taking care of yourself at the expense of others." This usage perpetuates the war between Oneself and Others.
But it could be argued that it simply means, "concern for one's self interest." It says nothing about sacrificing others for your interests.
And, in fact, if you consider your own self-interest both long-term and short-term, it is a rare situation in which a conflict will occur between taking care of yourself and taking care of others. Moreover, the best way to take care of yourself, short-term and long-term, is to take care of others, ensuring that your selfishness and their selfishness is symbiotic.